UX: details tag background colour (#24710)

plugins/discourse-details/assets/stylesheets/details.scss

@@ -1,5 +1,22 @@
 details {
   position: relative;
+  background-color: var(--primary-very-low);
+  padding: 0.25rem 0.75rem;
+  margin-bottom: 0.5rem;
+
+  &:not([open]) {
+    &:hover,
+    &:focus,
+    &:focus-within {
+      background-color: var(--d-hover);
+    }
+  }
+
+  aside.quote .title,
+  blockquote,
+  code {
+    background-color: rgba(var(--primary-rgb), 0.05);
+  }
 }
 
 details > *,
@@ -12,6 +29,13 @@ summary {
   outline: none;
 }
 
+summary {
+  > p {
+    margin-block: 0;
+    padding-block: 1rem;
+  }
+}
+
 summary:first-of-type {
   cursor: pointer;
   display: block;
@@ -43,6 +67,30 @@ summary::-webkit-details-marker {
 }
 
 .elided {
+  background-color: unset;
+  padding: 0;
+
+  &:not([open]) {
+    //specificity needed to overrule non-elided
+    &:hover,
+    &:focus,
+    &:focus-within {
+      background-color: unset;
+    }
+
+    summary:hover {
+      background: var(--d-hover);
+    }
+  }
+
+  &[open] {
+    background: var(--primary-very-low);
+    padding: 0.5rem 0.75rem;
+    summary {
+      padding: 0;
+    }
+  }
+
   summary:before {
     content: "" !important;
     display: none;
@@ -56,17 +104,17 @@ summary::-webkit-details-marker {
     text-align: center;
     box-sizing: border-box;
     margin: 0;
-    padding: 0;
+    padding: 0.5rem 0.75rem;
     color: var(--primary-medium);
-    background: var(--primary-low);
-    border: 1px solid var(--primary-low-mid);
-    width: 1.5em;
+    background: var(--primary-very-low);
+    width: min-content;
     line-height: 1;
-  }
 
-  summary:hover {
-    color: var(--primary);
-    background: var(--primary-low-mid);
-    border-color: currentColor;
+    &:hover,
+    &:focus,
+    &:focus-within {
+      color: var(--primary);
+      cursor: pointer;
+    }
   }
 }